In many industrial processes tanks or vessels are employed which are used either to store liquids for future use or in part of a process. Also, many types of vessels are used as the containment for a wide variety of reactions, both batch processes and continuous processes, each of which can result in deposits being made on the surfaces within the vessel. These deposits usually must be removed to  preserve the integrity of subsequent use of the vessel or tank. Most often, specific areas within a reaction vessel get significantly contaminated whereas other areas may have no contamination at all. Accordingly, one general object of the present invention is to use a limited amount of water or cleaning solvent to clean only the contaminated areas so that the waste cleaning liquid generated is a relatively small quantity to be discarded.
By way of an example, and not by way of limitation of the present invention, evaporators and specifically, evaporators that are used to reduce hazardous waste such as radioactive waste to a point where it can be effectively dealt with and disposed of present unique cleaning problems. Evaporators, boilers, and heat exchange equipment almost invariably leave deposits behind that require removal.
In one process, evaporators which consist of tanks or pots with warming coils are used to heat radioactive waste liquids until the liquid separates from the solids and is evaporated whereby the remaining liquid is concentrated liquid waste. A feed tank supplies the radioactive waste liquid that is pumped into an evaporator pot and into the pot's lower section which is conically-shaped. Warming coils are located in the conical section along with a steam lance and an intake line to a separator pot. Steam is introduced at the bottom of the conical section causing a decrease in the density of the waste material at the bottom of the evaporator pot. The heavier waste material above pushes down the less dense material and the  evaporator conical bottom is pushed up into the pipe to a separator pot leading to a feed tank that collects the more concentrated waste material.
The evaporators are housed in concrete boxes or cells with coils that surround the evaporators and associated jumper pipes. The cell covers are heavy concrete interlocking blocks. Access within the cell can be gained using riser ports in the cell covers that penetrate into the cell interior. However, removal of the cell cover from the base of the cell means that the cleaning liquid which may be sprayed up against the bottom of the cell cover will have to be collected and an additional area will have to be cleaned. Also, the floor of the cell can be cleaned directly under the access ports but, here again, in prior art cleaning devices excess liquid will be used that will cover the entire floor and it must be removed from the cell. Thus, it is much more effective and safer for the covers and flooring of such cells to be cleaned in place and not moved so that the liquids to be collected are kept at a minimum and the problem of containing them is significantly reduced.
Accordingly, it is another object of the present invention to provide a means for cleaning large heavy vessels with small access ports and perform the operation so that the risk of further contamination is significantly reduced.
Not only do vessels which contain radioactive materials need periodic cleaning but so do many vessels which contain a wide variety of products ranging from fuel oil to fertilizers to food products. In U.S. Pat. No. 3,599,871 which issued on Aug. 17, 1971 to Donald B. Ruppel et al., a jet spray cleaning apparatus is disclosed which directs a high pressure stream of fluid against the interior surface of  a tank that is used in chemical processing. However, the use of this cleaning apparatus requires a large man-way opening and multiple cantilevered arms which spray the entire surface inside a vessel leaving a large quantity of waste water. Thus, it is an object of the present invention to provide simplified equipment that can be inserted through small diameter access ports and direct high pressure spray at selected or identified areas within the interior of the vessel and use minimum cleaning water.
For another industry, the remotely-controlled, mounted robotic system of U.S. Pat. No. 5,740,821 which issued on Apr. 21, 1998 to Kermit R. Arnold is described for cleaning tanks used in the petrochemical oil refining industries. However, again, this device, though remotely guided, is a large cumbersome unit that can be used only where a manway is available. As stated above, a general object of the present invention is to provide a means for cleaning the interior of vessels and tanks through small access ports without large, cumbersome equipment which requires entry through manways. Other such prior art devices are disclosed in U.S. Pat. No. 4,201,597 which issued to James A. Armstrong, et al. on May 6, 1980; U.S. Pat. No. 5,179,757 which issued to Louis A. Grant, Jr. on Jan. 19, 1993; and U.S. Pat. No. 5,594,973 which issued to Joseph Brusseleers, et al. on Jan. 21, 1997.
Features of the present invention which accomplish its objects are described more fully below in the Summary of the Invention. 